Answer / sri krishna

the humming noise is due to the MAGNETOSTRICTION phenomenon.
the magnetostriction is caused due to the quik magnetic
reversals in ac circuit. magnentostriction is developed from
the words 'magnetic' 'restriction' implies the opposition of
the reversals of the magnetizing current.or simply..
oppozing the magnetizing and demagnetizing processes..
due to this some energy is lost in heat and some enrgy is
lost inthe form of sound but notice that sound was aktualy
produced by the minute vibration of the core and some other
metal parts. but we cant see this vibration wth our naked eye.

generally megentostriction does not okkurs in dc ckts.

Answer / amit

humming noise is a sound produced in power transmission line during the transmission of power.it is produced due to corona effect.it can be supresed by using stranded wires..

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